How to Make the Spawning of and Object Faster and Faster

So, I’m trying to get the greenLight to spawn faster and faster based on the amount of time the game has been active. I thought I could just have the delay on the time a variable and once the time hit’s a certain point then the variables value would change and the timer would recognize this. Right now I have the variable to change base on the score. Could someone please show me how to do it with the score as well as another version where I use time versus the score to determine the speed of the spawning. 

 Much Obliged . 

spawned = true – Spawn will equal true 

   greenLight = display.newImageRect( “greenLight.png”, 126, 126) ; – Render image to screen , One of the reasons this might be here is because when we remove the object from the screen we will want to genrate another one 

   greenLight.x = display.contentCenterX + columns[mRand(4)] — Randomly choos a column

greenLight.y = display.contentCenterY/ rows[mRand(4)] — Randomly choose a row 

function greenLight:touch( e )  – Add 1 to the score each tome the user touches the greenLight 

if(e.phase == “ended”) then 

audio.play(pop_sound)

score = score + 1

end

scoreLabel.text = score

end

greenLight:addEventListener( “touch”, greenLight ) – Calling the funtion for the score

function spawnGreen()

if(spawned == true) then  – Since Spawned is true we will : 

print(spawned)

greenLight.name = greenLight — Give image a name 

greenLight.x = display.contentCenterX + columns[mRand(4)] — Randomly choos a column

greenLight.y = display.contentCenterY/ rows[mRand(4)] — Randomly choose a row 

greenLightY = math.round(greenLight.y) – This is it’s Y position rounded , don’t want to work with insanely high numbers 

greenLightX = math.round(greenLight.x) – This is it’s X position rounded , don’t want to work with insanely high numbers 

–[[ The code below could possibly be the answer to the overlaping spawning problem with MOh2 

local greenLightCX , greenLightCY =  greenLight:localToContent( 0, 0 )

greenLightYActualPosition = mRound(greenLightCX)

greenLightXActualPosition  = mRound(greenLightCY)

–print( "The greenLights center position in screen coordinates: ", x, y )

x = 0

y = 0

prevX = greenLightXActualPosition

prevY = greenLightYActualPosition 

]]

end 

–if(5 == 5 ) then  — This was used when I wanted spawn to equal false 

– spawned = false 

–end 

–if(spawned == false ) then – When spawn equals false then the image will move around without drawing another image

– print( “…” )

— greenLight.x = display.contentCenterX + columns[mRand(4)]

  – greenLight.y = display.contentCenterY/ rows[mRand(4)]

–print( "The coordinates are           :  " … mRound(greenLight.x) … " " … mRound(greenLight.y) )

–end 

print( score )

end

delay = 1000

if score == 5 then 

delay = 8000

end 

spawner = timer.performWithDelay( delay, spawnGreen, -1 ) – 1 second, function, iterations